1. Technical Background
The present invention relates generally to medical devices, and more particularly to a balloon catheter having an improved tip design.
2. Discussion
Balloon catheters are used in a variety of therapeutic applications, including many vascular treatments such as angioplasty. Angioplasty can be used to treat vascular disease, in which blood vessels may be partially or totally blocked or narrowed by a lesion or stenosis. In many instances of vascular disease, a local area of a blood vessel may become narrowed. This narrowing is called a lesion or stenosis, and may take to form of hard plaque, cholesterol, fats, or viscous thrombus. Such a stenosis may cause heart attack or stroke, which are significant health problems affecting millions of people each year.
During angioplasty, an expansive force may be applied to the lumen of the stenosis, which may be a vessel constriction due to plaque buildup or thrombus, etc. This outward pressing of a constriction or narrowing at the desired site in a body passage is intended to partially or completely reopened or dilate that body passageway or lumen, increasing its inner diameter or cross-sectional area. The objective of this procedure is to increase the inner diameter or cross-sectional area of the vessel passage or lumen through which blood flows, to encourage greater blood flow through the newly expanded vessel.
As an example, the present invention will be described in relation to coronary, peripheral, and neuromuscular angioplasty. However, it should be understood that the present invention relates to any angioplasty catheter having the features of the present invention, and is not limited to catheters for a particular therapeutic procedure.
Some balloon catheters have a relatively long and flexible tubular shaft defining one or more passages or lumens, extending between a hub at a proximal end to a distal end where the balloon is located. The catheter shaft may define an inflation lumen for conducting inflation fluid from an inflation port defined by the proximal hub to selectively inflate or deflate the balloon, and may define a guidewire lumen extending from a distal guidewire port at the distal end of the catheter to a proximal port located at a position proximal from the balloon.
The guidewire lumen may be defined by a tubular inner body extending from a distal end of the catheter proximally through the entire length of the balloon. Whatever structural element defines the guidewire lumen, the inner diameter or cross-sectional area of the guidewire lumen is preferably large enough to accommodate the size of the desired guidewire. Likewise, the inner diameter of the guidewire lumen in the region of the balloon may preferably be constant, to facilitate easy movement of the guidewire within the guidewire lumen.
One possible shaft design is a coaxial arrangement of tubular inner and outer bodies, with a distal balloon leg affixed to the inner body, and a proximal balloon affixed to a distal end of the outer body.
During a common treatment method for using such a balloon catheter, a physician advances the catheter into the body of the patient, by directing the catheter distal end percutaneously through an incision and along a body passage, until the balloon is located within the desired site. The term xe2x80x9cdesired sitexe2x80x9d refers to the location in the patient""s body currently selected for treatment by a physician.
As the balloon catheter is advanced along the desired vascular path, the performance of the catheter design may be evaluated by analyzing various characteristics, including column strength, pull strength, flexibility, push ability, traceability, and cross ability. The term xe2x80x9ccross abilityxe2x80x9d usually refers to the ability to the catheter to successfully transmit pushing and guiding and steering forces applied at the proximal hub by the physician, such that the distal tip of the balloon catheter pushes into, through and past a constricted lesion. In addition, the desired performance of the balloon catheter enables it to follow a tortuous vascular path without injuring the vessel, prolapsing the guidewire or kinking. The term xe2x80x9ctraceabilityxe2x80x9d refers to the combination of characteristics that allows a catheter to follow the desired path.
As an example of prior balloon catheters, U.S. Pat. No. 5,891,110 entitled xe2x80x9cOver-The-Wire Catheter With Improved Traceability,xe2x80x9d issued to Lagoon et al. on Apr. 6, 1999 shows a balloon catheter having an inner tube with outer and inner walls that distally taper from larger diameters to smaller diameters, as well as an area adjacent to the balloon distal seal that is backfilled with adhesive to provide a smooth transition.
However, the present invention is improved over prior catheters, and relates to an improved tip design for a balloon catheter. One of the possible components of the present balloon catheter is a tubular inner body drawn down to reduce the outer dimension, but substantially maintain the inner lumen dimensions. This wall thickness optimization located inside the balloon preferably cooperates with a shaved and tapered distal leg of the balloon which is sealed to the inner tubular body forming a smooth and gentle leading-edge taper.
The catheter tip design should also preferably provide all of the desired performance characteristics, including flexibility with column strength. The present improved tip design may include the following novel features in combination: substantially constant guidewire lumen diameter, tubular inner and outer bodies, a wall thickness draw down of the inner body located between a marker band and the balloon distal leg seal, and a leading-edge taper of the distal balloon leg which is formed by shaving the balloon leg. The inner body distal end may also have a tip buff or end manicure to provide a gentle distal tip and to closely surround the guidewire.
These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings.